Add closed model in legends

src/display/about.py

@@ -136,6 +136,7 @@ To run our evaluations, checkout our [tutorial](https://github.com/AI-secure/Dec
 + 🔶 Fine-tuned Model: Pretrained model fine-tuned on more data
 + ⭕ Instruction-tuned Model: Models specifically fine-tuned on datasets with task instructions
 + 🟦 RL-tuned: Models specifically fine-tuned with RLHF or DPO
++ 🔒 Closed Model: Closed models that do not publish training recipies or model sizes
 
 If there is no icon, we have not uploaded the information on the model yet, feel free to open an issue with the model
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